Royal Dutch Shell, the oil group that runs one of the UK’s biggest, best-funded and most generous pension plans, is to restart payments of about £50m (€58m) a year into the fund following big losses in last year’s market meltdown.

Shell’s move to end a two-year holiday from its usual retirement contributions illustrates the scale of the damage that the credit crunch has done to pension schemes.

Most companies have concluded that generous final-salary benefits are unaffordable: IBM, Barclays and Shell’s rival BP have all announced plans this year to stop offering them to new joiners.

Shell is now one of only four companies in the FTSE 100 with open defined-benefit plans, and confirmed that it has no plans to shut its scheme.

But maintaining it will be costly. From this month, Shell has begun paying 31% of its workers’ salaries into the £10bn pensions pot, a strikingly high figure, according to pensions consultants. When Shell ceased contributions in July 2007, it was paying 17.7% of salary.

That cost the company £30.9m a year, and, extrapolating from that figure gives an estimate for Shell’s future pensions bill of £54.2m a year. A spokeswoman declined to comment on the amount.

Jerome Melcer, a partner at Lane Clark & Peacock, said: “If this is the cost of the ongoing benefits, and doesn’t include any special amounts to deal with a deficit, then it is certainly high even for a final-salary scheme.”

The Shell UK fund was in a narrow surplus at December 31, according to its most recent formal valuation, following a £2.5bn loss in the markets last year. At its last valuation three years ago, the scheme was 119% funded.

In a report to members, Shell’s pension trustees put last year’s losses down to overexposure to credit and small-cap stocks. With a one-year return of -16.5%, the scheme did better than the average performance of 50 leading UK schemes monitored by analysts WM Company, but undershot its internal targets.